EP0616460B1 - Public telephone apparatus - Google Patents

Description

Technical area

The present invention relates to an apparatus prepaid or postpaid telephone made available to public.

State of the art

Portable telecommunications terminals, such as microcomputers with communication card, are more and more widespread. Their owners want to be able to use them everywhere and in particular in "payphones" (registered trademark), which are pre- or post-payment telephones made available to the public.

To allow such use, payphones must be fitted with an external connection socket. Until this day, few possibilities were offered to users due to the risks of fraud presented by such an outlet.

• interface dédiée entre un publiphone et un terminal avec protection mécanique des différents accès à la ligne téléphonique;
• prise de connexion de terminaux externes sur les téléphones à cartes, dans lesquels où la sécurisation de la ligne téléphonique se fait par le réseau en acquittant en temps réel des unités de taxation émises par le commutateur de rattachement;
• prise de connexion de terminaux externes sur des publiphones installés en des lieux protégés, où la sécurisation de la prise est très limitée.

To date, the offer of a socket for connecting external terminals has only grown significantly for security reasons. The following solutions can nevertheless be cited:

• dedicated interface between a payphone and a terminal with mechanical protection of the various accesses to the telephone line;
• connection socket for external terminals on card telephones, in which the securing of the telephone line is done by the network by acknowledging in real time charging units sent by the home exchange;
• connection socket of external terminals on payphones installed in protected places, where the security of the socket is very limited.

In the case of a dedicated interface between a payphone of a particular type and a terminal of a particular type, line security is made "mechanically" by physical protection of all access to the telephone line. This kind of product is installed in direct view of the operator of the payphone. In addition, this kind of interface only works with a payphone of a particular type and a terminal of a particular type. We can cite as an example of implementation the device entitled "Point-Phone" (brand registered) and its interface for "Minitel" (registered trademark), which allows to obtain a "Publivideotex". It is not possible, for example, to connect to this kind of product produces a portable microcomputer equipped with a modem. Another example concerns the device called point-phone and a fax machine, which allows to obtain a "Publifax" (registered trademark). In both cases, the interface between the point-phone and the minitel or the fax machine is specific to each together.

In the case of a connection socket for external terminals on card phones, the telephone line is secured by real-time acknowledgment of the charging units sent by the exchange attachment. Between the card telephone and the home switch, a device is inserted in cutoff. At each charging pulse issued by the switch, the device interrogates the card telephone to ask if the tax has been received and charged to the card. In case of incorrect answer, the device cuts communication. The dialogue between the card telephone and the device is made by a supravocal connection outside the band telephone. Securing the socket for external terminal is then done by this super-vocal dialogue. It should be noted that in such a case security is not provided by the card phone but by the network to which this type of payphone.

In the event that the connection socket for external terminals is mounted directly on the public phone, security is limited. Thereby, the installation of this kind of public phone is done in protected places where the risks are minimized. Abroad, we can cite as an example of updating provision of the user with an outlet for an external terminal, the developed public phone by the company ATT installed mainly in airports in the United States.

To significantly develop the possibility of connect an external terminal to a payphone, it is necessary that the connection does not constitute a risk of non-payment of communications. To date, only two of the possibilities described above allow ordinary connection of external terminals to a socket.

In the case of the connection socket on the telephones to cards, it is necessary to have, on the premises of the switch attachment, a device for real-time monitoring of payment of communication. If this device offers all the necessary security, it the fact remains that the connection of this card telephone does not must not be done in any place, in the absence of the device supravocal, and that this card telephone does not correspond to all expressed needs.

In the event that the terminal connection socket mounted directly on the payphone, the potential risk of fraud is high. As a result, this type of public phone cannot be installed only when the monitoring of the public phone is ensured in permanently by the operator.

To solve these various problems, the invention has purpose of offering users a socket for external terminals on payphones which provides good immunity to fraud attempts without require the supravocal device mentioned above. Security must be brought by the public phone itself and not by the network.

A document of the prior art, the patent application French FR-A-2 607 343, describes a device for coupling a terminal telematics to a prepayment and / or payment telephone device deferred. This device connects access equipment to a service, such as than a videotex or fax terminal, to a telephone line when receives a request from a user transmitted by the access equipment. The connection request is only taken into account by this device if it receives from a prepaid and / or deferred payment telephone authorization signals indicating that the user has completed the communications payment operations and that a line can take place.

Statement of the invention

• une prise accessible à l'usager ;
• un circuit de gestion de cette prise ;
• un circuit de commutation permettant de basculer la ligne soit sur le circuit de gestion dudit appareil, soit sur le circuit de gestion de la prise ;
• un circuit d'information d'une connexion d'un terminal externe dans la prise ; le circuit de gestion de la prise étant relié d'une part au circuit de commutation par un premier module d'isolation galvanique, et d'autre part au circuit de gestion dudit appareil par un second module d'isolation galvanique.

To this end, the invention proposes a prepaid or postpaid telephone apparatus made available to the public comprising a management circuit connected to a telephone line, characterized in that it comprises:

• a socket accessible to the user;
• a circuit for managing this outlet;
• a switching circuit for switching the line either on the management circuit of said device, or on the outlet management circuit;
• an information circuit of a connection of an external terminal in the socket; the outlet management circuit being connected on the one hand to the switching circuit by a first galvanic isolation module, and on the other hand to the management circuit of said device by a second galvanic isolation module.

Advantageously, the device of the invention comprises a external terminal supply circuit which can either be internal to the payphone, and connected to the outlet management circuit through a third galvanic isolation module, either external and placed between the external terminal and socket.

The information circuit of a connection can be a current detector circuit, or an external switch manipulated by the user.

In a particularly exemplary embodiment advantageous, the galvanic isolation modules each include a transformer. An alternative power source is connected to a circuit current regulator through a transformer and a bridge diodes, this regulator having its output inserted between two windings of the transformer producing the first galvanic isolation module. The current regulator circuit includes a transistor, two resistors and a diode; a first ability to close the flow laternative, a second capacity allowing to smooth the direct current.

Advantageously, the current detector is produced by an optocoupler, a capacity allowing the passage of currents alternative.

In an alternative embodiment, the device of the invention includes an amplification set composed of a passage module two wires-four wires, two amplifiers for two wires respectively in one direction of transmission and in the other, and a passage module four sons-two sons.

In a digital variant embodiment, the circuit public phone management includes a coding-decoding circuit and a line interface circuit connected to the telephone line, a two-wire module wires being inserted between the first galvanic isolation module and the switching circuit which switches the management circuit of the public telephone connected to the line either on the socket or on the handset.

Advantageously, the invention makes it possible to produce a device connection between an external terminal, which can for example be a portable microcomputer, portable fax machine, portable minitel, post cell phone, and a payphone ensuring good immunity to fraud attempts without using a super-voice device, which requires a dialogue link, in a frequency outside the band telephone, between the external terminal and the payphone. Security, in the device of the invention, is provided by the payphone itself and not by the network.

• immunité au masquage des impulsions de taxation par des perturbations qui pourraient être générées par un usager mal intentionné (dans le cas où la taxation s'effectue par impulsions émises par le commutateur) ;
• contrôle de la prise de ligne téléphonique par le publiphone et non par le terminal externe. Cette fonction est nécessaire dans tous les modes de calcul de taxation ;
• contrôle de la numérotation par le publiphone dans le cas où il existe des restrictions pour l'appel de certains numéros.

To eliminate any possibility of fraudulent use of the socket, the invention provides the following functions:

• immunity to masking of charging pulses by disturbances which could be generated by a malicious user (in the case where charging is carried out by pulses sent by the exchange);
• control of the telephone line taken by the public phone and not by the external terminal. This function is necessary in all taxation calculation modes;
• control of the dialing by the public phone in case there are restrictions for calling certain numbers.

The solution presented is particularly interesting in the event that the charge for the call is calculated and then issued by the home switch. In France, the impulses for taxation are issued from the home switch to the public phone as sending frequencies at 12 kHz for a hundred milliseconds. In other countries, the frequency may be 16 kHz. In case the calculation of the taxation is carried out locally by the payphone, the invention remains usable and also improves immunity to fraud.

Brief description of the figures

• Figure 1 illustrates the device of the invention;
• Figure 2 illustrates a particular embodiment of the device the invention;
• Figures 3 to 5 illustrate three alternative embodiments of the device of the invention.

Detailed description of the embodiments

• une prise 15 accessible à l'usager ;
• un circuit de gestion de cette prise 16 relié :
  • aux deux fils a et b d'une ligne téléphonique 20 au travers d'un premier module d'isolation galvanique 21 et d'un circuit de commutation 22 qui permet, lorsque le circuit de gestion 10 du publiphone détecte le branchement d'un terminal extérieur 14 dans cette prise 15, de basculer la ligne 20 qui était branchée à ce circuit de gestion du publiphone 10 sur la prise 15,
  • au circuit de gestion du publiphone 10 au travers d'un second module d'isolation galvanique 19,
  • à un circuit d'alimentation 17 du terminal externe au travers d'un troisième module d'isolation galvanique 18.

As shown in FIG. 1, the device of the invention interfaces on the one hand with the circuits constituting a payphone 9 which are in particular a management circuit 10, to which can be connected, for example, a memory card reader 8, a display 11, a telephone handset 12 and a davit 13, and on the other hand an external terminal 14, comprises:

• a socket 15 accessible to the user;
• a management circuit for this socket 16 connected:
  • to the two wires a and b of a telephone line 20 through a first galvanic isolation module 21 and a switching circuit 22 which allows, when the management circuit 10 of the public telephone detects the connection of a terminal outside 14 in this socket 15, to switch the line 20 which was connected to this management circuit of the public phone 10 on socket 15,
  • to the management circuit of the public phone 10 through a second galvanic isolation module 19,
  • to a supply circuit 17 of the external terminal through a third galvanic isolation module 18.

A possible tax receiver 23 can be integrated into the payphone between the two wires a and b of the telephone line 20.

The device of the invention enables the connection between the external terminal and the circuits constituting the payphone, with installation of a connection socket for said external terminal.

Figure 2 illustrates a particular embodiment of the device. The invention In this figure, circuits similar to those of FIG. 1 have kept the same reference.

The power circuit 17 is a power source alternative connected through the third galvanic isolation module 18, produced here by a transformer, to a rectifier diode bridge 24 of which two branches are connected to a current regulator circuit 25 formed by a transistor T1, two resistors R1 and R2 and a diode D3: a first capacity C1 allowing the passage of alternative signals and a second C2 capacity to smooth the direct current.

The first galvanic isolation module 21 includes a double insulated transformer to balance the line in injecting current into the middle.

The second galvanic isolation module 19 is produced by a optocoupler, the third capacitance C3 making it possible to avoid a weakening of the alternating current.

Two diodes D1 and D2, arranged head to tail, allow to clip the very high level signals that we would like to introduce on the socket 15. D4 and D5 diodes protect line 20.

The connection of an external terminal 14 to socket 15 is detected by monitoring for the appearance of direct current.

• l'isolation galvanique ;
• l'alimentation locale ;
• le détecteur de courant.

In this exemplary embodiment shown in FIG. 2, the device of the invention therefore fits into a payphone having an external power supply. The three constituent elements of the basic principle are found in the realization:

• galvanic isolation;
• local food;
• the current detector.

The galvanic isolation is carried out by a transformer whose bandwidth is equivalent to that of the telephone band, i.e. 300 Hz to 3400 Hz.

Local food is produced from a source of continuous voltage. The ballast-mounted transistor T1 limits the direct current in case of short circuit of the two pads of the socket 15 for external terminals. This power supply is generated from an alternating voltage source 17 at through transformer 18 exclusively reserved for this purpose in order to preserve galvanic isolation. The power supply is inserted between two windings of the transformer 21 to ensure good symmetry. The capacity C1 allows the passage of alternative signals. In the case of this realization, it is considered that the payphone has an external power supply in addition to its remote power supply by line. This case corresponds to a large number of implementation possibilities and is consistent with the type of payphones which will have this socket 15.

The current detector 19 is produced with an optocoupler which informs the public phone of the closure of socket 15 by a terminal 14. The capacity C3 allows the passage of alternative signals. Galvanic isolation is preserved.

The proposed scheme prevents any action from breaking the loop direct on the telephone line. However, it allows the transmission of all signals in the 300 - 3400 Hz band when the telephone line is oriented towards the connection socket of external terminals.

To limit the level of the alternative signals to be transmitted on the telephone line, the two head-to-tail diodes D4 and D5 clip any signal alternative above a certain level.

Likewise to limit disruption on the line, the transformer has a role of filtering frequencies outside the band telephone. If necessary, a passive filter can be introduced at the outlet input.

• une isolation galvanique assure la séparation entre le terminal externe et le publiphone ;
• une alimentation locale simule pour le terminal externe un raccordement sur un commutateur. Cette alimentation est nécessaire pour permettre le fonctionnement de tout terminal externe ;
• un détecteur de courant permet de surveiller le raccordement sur la prise 15 d'un terminal 14 en mode communication. Cette fonction n'est pas indispensable mais permet d'offrir à l'usager un mode de fonctionnement plus simple.

To secure this link and to ensure the functions described above, the invention therefore has the following characteristics:

• galvanic isolation ensures separation between the external terminal and the payphone;
• a local power supply simulates for the external terminal a connection on a switch. This power supply is necessary to allow the operation of any external terminal;
• a current detector makes it possible to monitor the connection to the socket 15 of a terminal 14 in communication mode. This function is not essential but makes it possible to offer the user a simpler mode of operation.

The payphone receiver for the public phone 23, when it exists, is always at the entrance to the public phone 9 to monitor, in all phases and at any time, the arrival of tax units.

• un rôle d'immunité vis-à-vis de certaines tentatives de fraude ;
• un rôle d'interdiction de prise de ligne téléphonique 20 par le terminal 14. Celle-ci ne peut se faire que par le publiphone.

The role of the galvanic isolation is to ensure an electrical separation between the two contacts of the connection socket 15 and all the electronics of the public phone. This isolation must allow a bandwidth equivalent to that of the telephone band, that is to say from 300 Hz to 3400 Hz. This galvanic isolation actually fulfills two roles:

• immunity from certain fraud attempts;
• a role of prohibiting the taking of a telephone line 20 by the terminal 14. This can only be done by the public telephone.

Local power supply for the external terminal 14 is carried out at from an energy source which must be isolated galvanically from both the telephone line 20 and the power supply general of the payphone. This supply is included in values of voltage and current which simulate a connection on a telephone line. A current limiting device is present to eliminate all risks of deterioration of the external terminal or danger to the user.

A current detector allows monitoring of the connection of an external terminal to the socket. This detector must also be galvanically isolated from the electronics of the payphone. The function of this detector is to recognize the presence of direct current in the outlet, that is, to be informed that the external terminal is in a loop. he can also be used to detect decimal dialing attempts that could transmit the connected terminal.

The socket for the external terminal has two pins connection. this grip is made of material strong enough to resist various attacks.

To ensure the level of security required to extend the public phone park equipped with a connection socket for external terminals, the device of the invention must be integrated into the public phone. He must do the connection between the external terminal and the constituents of the public phone. The operation of this device is described below in the different phases of a telephone call from a payphone.

• par appui sur une touche spécifique 26 sur le publiphone ;
• par connexion automatique, lorsque le publiphone sait détecter la présence d'un terminal externe 14.

When the line is taken, which is the consequence of the handset being lifted by the user, the operation of the payphone in telephone mode does not change. When a connection socket for external terminal 14 is present, switching to this external terminal can be carried out in two ways:

• by pressing a specific key 26 on the public phone;
• by automatic connection, when the public phone can detect the presence of an external terminal 14.

These two solutions can either be present both on the same payphone, either exclusive, depending on the functions you want offer to the user.

When connecting an external terminal, the public phone is informed of the connection request either by a presence detector on socket 15, either by pressing the connection key 26.

This request is only taken into account if a means of valid payment is present in the payphone. If the payment method is valid, the actual line seizure is made by the public phone.

Telephone line 20 is immediately switched to the external terminal 14 through galvanic isolation 21 if the numbering must be done by the external terminal. Otherwise the changeover takes place only after numbering.

The next phase is the dialing phase. The numbering can be issued either by the public phone or by the terminal external. These two possibilities can be offered simultaneously or not on the payphone. In particular, dialing by the external terminal 14 may be prohibited for security reasons.

Dialing can therefore be carried out by the public phone. This case is the simplest and is most suitable when employment restrictions vis-à-vis certain numbers exist. It provides a priori the best security. The dialing of the only authorized numbers is then ensured since it is the payphone that manages everything. No frequency can be transmitted on the line by terminal 14 before the end of dialing because the connection towards the socket is cut. At the end of the numbering, the link to socket 15 is established and the external terminal can go into conversation phase.

• s'il n'y a pas de restrictions d'emploi vis-à-vis de certains numéros, la numérotation à fréquences vocales peut être transmise directement au réseau téléphonique via l'interface. Si la numérotation décimale doit aussi pouvoir être utilisée, un détecteur de courant reconnaít la numérotation décimale puis le publiphone renumérote sur la ligne téléphonique pour transmettre le numéro car il y a isolation galvanique entre le terminal externe et cette ligne. Cette renumérotation peut être soit décimale, soit en fréquence vocale ;
• si des restrictions d'emploi vis-à-vis de certains numéros existent, la surveillance de la numérotation est en plus indispensable. En numérotation décimale, celle-ci peut se faire à l'aide du détecteur de courant. En numérotation à fréquence vocale, la surveillance doit se faire à l'aide d'un circuit de détection de fréquences vocales intégré à cette interface tout en gardant bien sûr un isolation galvanique. En cas de détection d'un numéro interdit, la communication est interrompue. Si le numéro est autorisé, la numérotation est émise comme précédemment.

Dialing can also be carried out by the external terminal 14. This case is more complex to manage:

• if there are no usage restrictions for certain numbers, voice frequency dialing can be transmitted directly to the telephone network via the interface. If decimal numbering must also be able to be used, a current detector recognizes decimal numbering and then the renumbered public phone on the telephone line to transmit the number because there is galvanic isolation between the external terminal and this line. This renumbering can be either decimal or in voice frequency;
• if there are restrictions on the use of certain numbers, monitoring the numbering is also essential. In decimal numbering, this can be done using the current detector. In voice frequency dialing, monitoring must be done using a voice frequency detection circuit integrated into this interface while, of course, maintaining galvanic isolation. Communication is interrupted if a prohibited number is detected. If the number is authorized, the numbering is transmitted as before.

In the conversation phase, the user can use his external terminal 14 and transmit all frequencies in the band telephone. The telephone line 20 is oriented towards the external terminal 14 through galvanic isolation 21. Local power supply simulates a line real telephone number for the external terminal. Current detector ensures the presence of the external terminal.

Immunity to fraud is ensured by galvanic isolation which prevents from disturbing the telephone line.

• sur ordre du publiphone, en cas d'épuisement du crédit par exemple ;
• par rupture de la communication par le terminal externe dans les cas suivants :
  • lorsque l'usager débranche le terminal de la prise externe,
  • lorsque le terminal externe rompt la boucle continue sur la prise (équivalent à un raccroché de ligne). Le détecteur de courant en informe le publiphone qui libère à ce moment la ligne téléphonique réelle.

The end of the communication can be caused:

• on the order of the public phone, in the event of exhaustion of the credit for example;
• by breaking the communication by the external terminal in the following cases:
  • when the user disconnects the terminal from the external socket,
  • when the external terminal breaks the continuous loop on the socket (equivalent to a line hang-up). The current detector informs the public phone, which then releases the real telephone line.

In some cases, the payphone offers a possibility of "credit recovery" either by performing a short hang-up, or by pressing a specific touch. This facility can be preserved with the connection-external socket. In this case after having recognized a request for "credit recovery" by the user, the payphone opens a line to release the switch equipment then loops the line. The cycle of a normal communication can then resume.

We can then consider several variant embodiments of the device of the invention.

In the event that the attenuation is too strong between taking 15 of external connection and telephone line 20, signal amplification is introduced. This amplification is done on the payphone side for eliminate problems of galvanic isolation. One passage fitting two wire-four wire is made to amplify the signal in each direction. For the connection to the telephone network, the connection is made on the speech circuit of the payphone. Thus in a first alternative embodiment, shown in the FIG. 3, an amplification assembly is inserted between the transformer 21 and the switching circuit 22. It includes a module 30 for two passage wires-four wires, two amplifiers 30 and 31 for two wires respectively in one direction of transmission and in the other, and a module 33 of passage four son-two sons.

In case there is no external power supply for the payphone, supplying local power for the payphone becomes difficult for reasons of energy balance of the payphone. Under these conditions, the solution is that the user has a specific cord between the taking the public phone and its external terminal. This specific cord generates a power source from cells or batteries. This current source replaces the local power supply described in the basic diagram, the rest do not not changing. Galvanic isolation is ensured because the power comes from from an independent external source. So, in a second variant shown in Figure 4 the user must interpose a specific box 34 comprising a power supply 35, between its terminal 14 and the socket 15.

The operating modes described above concern analog payphones where securing access to the line telephone is essential.

In the case of a digital payphone, taking connection for analog external terminals is carried out in the same way. In this case the part of the device of the invention taken side does not change. The part of this device on the public phone side, on the other hand, is evolving. At the end of transformer 21, a telephone signal digitization circuit allows the digital broadcast on line 20 through the public phone interface. This circuit also transforms the signals received from the line via the public phone into a signal analog transmitted to the socket via the transformer. A third variant digital is shown in Figure 5. The management circuit of the public phone 10 then comprises a coding-decoding circuit 36 and a line interface circuit 37. A two-wire-four-wire module 38 is interposed between the first module galvanic isolation 21 and the switching circuit 22 which allows switching the management circuit of the public phone 10 connected to the telephone line either on the socket 15, ie on the handset 12. The operating principles of the the invention taken side remain identical. Dialing from the terminal external can be considered in the same way as in the case of the payphone analog with digital renumbering by the public phone.

Claims (12)

1. Prepayment or postpayment telephone apparatus made available to the public comprising a control circuit (10) connected to a telephone line (20), characterized in that it comprises:

   a connector (15) accessible to the user,

   a circuit (16) controlling said connector (15),

   a switching circuit (22) making it possible to switch the line (20) either to the control circuit of said apparatus (10) or to the control circuit (16) of the connector (15),

   an information circuit (12) of a connection of an external terminal in the connector (15),

   the connector control circuit being connected on the one hand to the switching circuit (22) by a first electrical insulation module (21) and on the other to the control circuit of said apparatus (10) by a second electrical insulation module (19).
2. Device according to claim 1, characterized in that it comprises a power supply circuit for the external terminal.
3. Device according to claim 2, characterized in that the power supply circuit (17) is within the public telephone and is connected to the control circuit of the connector (16) across a third electrical insulation module (18).
4. Device according to claim 2, characterized in that the power supply circuit is an external box (34), which can be placed between the external terminal (14) and the connector (15).
5. Device according to claim 1, characterized in that the information circuit of a connection is a current detector circuit.
6. Device according to claim 1, characterized in that the information circuit of a connection is an external switch (26), which can be manipulated by the user.
7. Device according to any one of the preceding claims, characterized in that the electrical insulation modules (18, 19, 21) in each case comprise a transformer.
8. Device according to claim 7, characterized in that it comprises an a.c. power supply (17) connected to a current regulating circuit (25) across a transformer (18) and a diode bridge (24), said regulator having its output inserted between two windings of the transformer constituting the first electrical insulation module.
9. Device according to claim 8, characterized in that the current regulating circuit comprises a transistor (T1), two resistors (R1,R2) and a diode (D3), a first capacitor (C1) making it possible to loop the alternating current and a second capacitor (C2) making it possible to smooth the direct current.
10. Device according to claim 5, characterized in that the current detector is constituted by an optical coupler (19), a capacitor (C3) permitting the passage of alternating currents.
11. Device according to claim 1, characterized in that it comprises an amplifying unit (29) formed by a two wire - four wire passage module (30), two amplifiers (31,32) for two wires respectively in one transmission direction and in the other, and a four wire - two wire passage module (33).
12. Device according to claim 1, characterized in that the public telephone control circuit comprises an encoding-decoding circuit (36) and a line interface circuit (37) connected to the telephone line (20), a two wire-four wire module (38) being inserted between the first electrical insulation module (21) and the switching circuit (22) making it possible to switch the public phone control circuit (10) connected to the line either to the connector (15), or to the hand set (12).

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